The present study compared the safety and efficacy of intra- and supra-annular self-expanding THVs for TAVI in patients with severe AS and yielded the following main findings: First, the implantation of both THVs was safe, and severe adverse events occurred with comparable frequency until discharge. Second, the Navitor THV group showed a lower risk of moderate or severe PVL and a similar mean pressure gradient compared with Evolut THV. Third, mid-term mortality was comparable between both groups. Fourth, the estimated risk of coronary obstruction after redo-TAVI was lower in the Navitor than in the Evolut THV group.

In the present study, in-hospital and mid-term mortality were 2% and 22% after Navitor THV implantation and 3% and 19% after Evolut THV implantation, respectively. In-hospital and mid-term mortality were comparable between the THV groups but slightly higher than in previous studies of intra- or supra-annular SEVs in small aortic annuli, which reported an in-hospital mortality of 1% and a two-year mortality of 14% and 15% for intra- and supra-annular SEVs, respectively [17, 18]. Campanella et al. compared Navitor and Evolut platforms (R, PRO, and FX) and observed a six-month survival of 92 ± 4% following Navitor and 93 ± 2% following Evolut THV implantation [19]. The differences in mortality may be explained by lower average left ventricular ejection fraction, the more frequent occurrence of significant concomitant mitral regurgitation, and the higher prevalence of comorbidities such as coronary artery disease and chronic obstructive pulmonary disease in the present study [17].

In both groups, in-hospital adverse events during and after TAVI were low and comparable to previous studies [18]. A significantly higher rate of major vascular complications and bleeding events according to BARC criteria, but not according to VARC, was observed after Navitor THV. However, we could not find an increased risk for the combined primary safety endpoint after Navitor THV, which is in line with a previous study including Navitor, Evolut R, PRO, and FX THV [19]. Permanent pacemaker implantation occurred in 17% of patients after Navitor THV and 18% of patients after Evolut implantation. A similar incidence of pacemaker implantation was reported by Campanella et al., with higher rates also observed after Evolut THV implantation (Navitor THV 13% vs. Evolut THV 16%) [19].

In the present study, patients with a Navitor THV showed a significantly lower risk of a moderate or severe PVL compared with patients with an Evolut THV (0.8% vs. 3.5%). In both groups, the prevalence of at least moderate PVL was low compared to previous studies. Yamamoto et al. observed at least moderate PVL in 2.8% of the intra-annular THV group and in 4.5% of the supra-annular THV group, which was a significant difference before but not after propensity score matching [18]. Another study also demonstrated a comparable frequency of PVL in intra-annular SEVs (Portico, Navitor) and supra-annular (CoreValve, Evolut R, Evolut PRO, Evolut PRO +, Evolut FX) [17]. Campanella et al. detected a similar rate of PVL after Navitor THV implantation compared with the Evolut THV, including Evolut R, PRO, and FX [19]. This is noteworthy, as the Evolut R prosthesis is not covered by an outer skirt, leading to comparable PVL in that study [19]. However, for this reason, we excluded the Evolut R platform and focused on Evolut PRO and PRO +. The Navitor and the Evolut THV groups showed comparable pressure gradients after implantation, although the aortic valve annulus area and perimeter at baseline and the implanted THVs were larger in the Evolut than in the Navitor group. Previous studies in patients with small aortic annuli reported differences regarding the gradient after TAVI: the intra-annular Navitor THV was associated with similar postprocedural effective orifice area, but higher pressure gradient compared with the supra-annular Evolut FX THV [18]. Other studies showed similar pressure gradients when comparing (i) different intra-annular (Portico, Navitor) and supra-annular SEVs (CoreValve, Evolut R, Evolut PRO, Evolut PRO +, and Evolut FX), but also (ii) Navitor THVs and Evolut THV (R, PRO, and FX), and suggested that the self-expandable feature and the cylindric inflow design of the Navitor THV enable supra-annular-like gradients despite its intra-annular position [17, 19].

With the expansion of TAVI to younger patients, lifetime management including preserved coronary access after redo-TAVI is becoming essential [20]. Approximately 10% of patients after TAVI experience at least one acute coronary syndrome in the first two years, and in 8% of patients, coronary cannulation post-TAVI is not possible [21, 22]. For a comprehensive comparison of Navitor and Evolut THVs, we calculated the risk of coronary obstruction using the heights of the RCA and LCA from CT measurements, the implantation depth of the THVs from fluoroscopy, and the height of a potentially implanted S3 THV. Overall, the Navitor THV presented a lower risk of the neoskirt reaching above the coronary risk plane compared with the Evolut THV. However, as further parameters influencing coronary obstruction after redo-TAVI were not considered, such as the relation of the THV to the sinus of Valsalva, design features, commissural alignment, and leaflet calcification, the risk can only be estimated [22,23,24,25,26]. Nevertheless, our results are in line with a previous study showing that supra-annular SEVs (Evolut) were associated with a higher risk of coronary obstruction compared with intra-annular SEVs [27]. The taller leaflet neoskirt due to the higher implantation depth increases the risk of coronary obstruction in redo-TAVI procedures [27]. In contrast, leaflet overhang is reduced in cases of low implantation.

The present study has a few limitations. First, the study is limited by its retrospective design; data were not blinded, and patients were not randomized. Adjusted regression analysis was used to account for imbalances between both groups. Second, prospective long-term data were not available for all patients.

To conclude, the implantation of the intra-annular self-expanding Navitor THV and the supra-annular self-expanding Evolut THV appears safe, and severe adverse events occurred with comparable frequency until discharge. The risk of moderate or severe PVL was lower in the Navitor THV group, and mid-term mortality was low and comparable in both groups.